Charging device and charging method

ABSTRACT

A charging device for charging a battery ( 10 ) by an external power supply ( 2 ) includes a temperature sensor ( 46 ) for detecting the temperature of the battery, a charger ( 4 ) receiving electric power from the external power supply to charge the battery, and a control device ( 50 ) controlling the charger such that the battery is charged at a charging rate determined based on the temperature difference between a charging/discharging limitation start temperature and the battery temperature. Preferably, the control device ( 50 ) determines the charging rate based on the difference between the amount of charge corresponding to full charge of the battery ( 10 ) and the current remaining amount of charge, and the temperature difference. Preferably, the vehicle ( 100 ) on which the battery ( 10 ) is mounted repeatedly carries out charging and vehicle-running. The control device ( 50 ) determines the charging rate according to the temperature increase expected amount when the vehicle runs next time.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national phase application of InternationalApplication No. PCT/JP2011/059902, filed Apr. 22, 2011, the content ofwhich is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a charging device and charging methodfor a vehicle-mounted battery, particularly to a charging device and acharging method for charging a vehicle-mounted battery by an externalpower supply.

BACKGROUND ART

In recent years, electric vehicles and hybrid vehicles are attractingattention as environment-friendly vehicles. An electric vehicle has avehicle-mounted battery charged from an external source. Furthermore,research efforts are now being made to allow a vehicle-mounted batteryto be charged from an external source in some hybrid vehicles.

When a vehicle-mounted battery is to be charged from an external source,the time required for charging becomes an issue. Charging must becarried out with high-amperage current to reduce the time required forcharging.

Japanese Patent Laying-Open No. 2002-233070 (PTL 1) discloses a batterycharging device that allows charging in a short time even if thetemperature of the battery is increased during rapid charging.

CITATION LIST Patent Literature

-   PTL 1: Japanese Patent Laying-Open No. 2002-233070-   PTL 2: Japanese Patent Laying-Open No. 2002-204538-   PTL 3: Japanese Patent Laying-Open No. 2002-165380

SUMMARY OF INVENTION Technical Problem

Under the circumstances where the cost and the weight of the battery arestill great, it is difficult to mount on a vehicle a battery having thecapacitance that allows the vehicle to run for a long distance withoutauxiliary charging. There is the need to additionally charge the batterywhen running for a long distance. Since it is desirable to terminatecharging that is carried out during the travel towards a destination ina short period of time, charging is carried out with high-amperagecurrent.

A cooling device is provided since the battery rises in temperatureduring charging as well as during vehicle-running. The cooling device isgenerally designed to accommodate the heat generated duringvehicle-running. The continuous flow of high-amperage current in rapidcharging causes heat to be generated greater in amount than thatgenerated during vehicle-running. However, if the cooling device isdesigned to comply with rapid charging, the cooling device will becomelarger in size, leading to increase in weight, cost, and volume. This isnot practical for a vehicle.

If rapid charging and vehicle-running are carried out repeatedly, thetemperature of the battery will rise. When the temperature of thebattery reaches a predetermined value, charging and discharging will berestricted in the aspect of protection as compared to a usual state.

An object of the present invention is to provide a charging device andcharging method that allows charging and discharging to be carried outwhile avoiding limitation by suppressing temperature increase of avehicle-mounted power storage device.

Solution to Problem

The present invention is directed to a charging device for charging abattery mounted on a vehicle by an external power supply. The vehicle isconfigured to increase limitation on electric power that is charged toand discharged from the battery according to increase in batterytemperature, when the battery temperature exceeds a predeterminedtemperature. The charging device includes a temperature sensor fordetecting a temperature of the battery, a charger receiving electricpower from an external power supply to charge the battery, and a controldevice controlling the charger such that the battery is charged at acharging rate determined based on a temperature difference between thepredetermined temperature and the battery temperature.

Preferably, the control device determines the charging rate based on thedifference between an amount of charge corresponding to full charge ofthe battery and the current remaining amount of charge, and thetemperature difference.

Preferably, the vehicle on which the battery is mounted is capable ofrepeatedly executing a charging operation towards the battery fromoutside the vehicle and a vehicle-running operation. The control devicedetermines the charging rate based on the expected amount of temperatureincrease when the vehicle runs next time and the temperature difference.

Another aspect of the present invention is directed to a charging methodfor charging a battery mounted on a vehicle by an external power supply.The vehicle is configured to increase limitation on electric powercharged to and discharged from the battery according to increase inbattery temperature when the battery temperature exceeds a predeterminedtemperature. The charging method includes the steps of detecting batterytemperature, calculating the temperature difference between thepredetermined temperature and the battery temperature, and charging thebattery such that charging of the battery is executed at a charging ratedetermined based on the temperature difference.

Preferably the charging step determines the charging rate based on thedifference between an amount of charge corresponding to full charge ofthe battery and the current remaining amount of charge, and thetemperature difference.

Preferably, the vehicle on which the battery is mounted is capable ofrepeatedly executing a charging operation towards the battery fromoutside the vehicle and a running operation.

The step of charging determines the charging rate based on the expectedamount of temperature increase when the vehicle runs next time and thetemperature difference.

Advantageous Effects of Invention

According to the present invention, charging and discharging can becarried out while suppressing temperature increase of a vehicle-mountedpower storage device, as well as allowing long-distance running.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an entire block diagram of an electric powered vehicleaccording to an embodiment of the present invention.

FIG. 2 is a diagram to describe a configuration of a vehicle related tocooling of the power storage device in FIG. 1.

FIG. 5 represents a comparison on battery temperature increase betweenthe case where charging is carried out according to the charging methodof the present invention and the case where charging is carried outwithout applying the present invention.

FIG. 3 is a flowchart to describe the process in a charging methodexecuted in the first embodiment.

FIG. 4 represents an exemplary map employed in determining chargingcurrent at step S5.

FIG. 6 is a flowchart to describe the process in a charging methodexecuted in the second embodiment.

FIG. 7 represents an exemplary map employed in determining chargingcurrent at step S17.

FIG. 8 is a flowchart to describe the process in a charging methodexecuted in a third embodiment.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described in detail withreference to the drawings. In the drawings, the same or correspondingelements have the same reference characters allotted, and descriptionthereof will not be repeated.

First Embodiment

FIG. 1 is an entire block diagram of an electric powered vehicleaccording to an embodiment of the present invention.

Referring to FIG. 1, an electric powered vehicle 100 includes a battery10, an inverter 20, a motor generator 30, and a driving wheel 35.Electric powered vehicle 100 further includes a voltage sensor 42, acurrent sensor 44, a temperature sensor 46, a wheel speed sensor 37, anelectric control unit (ECU) 50, a display device 60, a navigation device6, an intake air temperature sensor 45, and a charger 4. Intake airtemperature sensor 45 measures the intake air temperature of the coolingdevice that cools battery 10, as will be described afterwards withreference to FIG. 2.

Battery 10 is a DC power supply storing the electric power for thevehicle to run. Battery 10 is formed of a secondary battery such as anickel-metal hydride battery, a lithium ion battery, or the like.Battery 10 is charged by a power supply external to the vehicle by meansof charger 4. Charger 4 may be mounted on the vehicle, or may beinstalled outside. Battery 10 is charged quickly by a power supply 2installed at a charging station or the like.

In addition, battery 10 is charged by the electric power generated atmotor generator 30 via inverter 20 during a braking operation ofelectric powered vehicle 100 or at the time of reduction in accelerationsuch as when running down a slope.

Battery 10 outputs the stored electric power to inverter 20. Inverter 20converts the DC power supplied from battery 10 into 3-phase AC foroutput to motor generator 30, based on signal PWI from ECU 50 to drivemotor generator 30.

During braking or the like of electric powered vehicle 100, inverter 20converts the 3-phase AC power generated by motor generator 30 intodirect current based on signal PWI, and outputs the converted electricpower to battery 10. Inverter 20 is formed of a 3-phase PWM inverter,for example, including switching elements of three phases.

Motor generator 30 is a motor generator capable of a power runningoperation and a regenerative operation. Motor generator 30 is formed ofa 3-phase AC synchronous motor generator having a permanent magnetembedded in the rotor. Motor generator 30 is driven by inverter 20 togenerate the traction drive torque to drive driving wheel 35. In thebraking operation of electric powered vehicle 100, motor generator 30receives the kinetic energy of electric powered vehicle 100 from drivingwheel 35 to generate power.

Voltage sensor 42 detects a voltage VB of battery 10 to output thedetected value to ECU 50. Current sensor 44 detects a current IB inputto and output from battery 10, and outputs the detected value to ECU 50.Temperature sensor 46 detects a temperature TB of battery 10 to outputthe detected value to ECU 50. Wheel speed sensor 37 outputs a pulsegenerated in accordance with the rotational angle of driving wheel 35.The number of the pulses can be counted by ECU 50 to allow calculationof the running distance L and vehicle speed. As an alternative to wheelspeed sensor 37, the rotation speed of motor generator 30 can bedetected to obtain the travel distance and/or vehicle speed.

ECU 50 receives the detected values of voltage VB, current IB andtemperature TB from voltage sensor 42, current sensor 44 and temperaturesensor 46, respectively. Then, ECU 50 generates a PWM signal directed todriving inverter 20, and outputs the generated PWM signal to inverter 20as a signal PWI.

ECU 50 calculates the state of charge (SOC: also called charging state,remaining amount, and amount of charge) of battery 10 based on thedetected values of voltage VB and current IB. The SOC can be calculatedusing various well-known methods such as the calculation method usingthe relationship between the open circuit voltage (OCV) and the SOC ofbattery 10, or the calculation method using the accumulated value ofcurrent IB.

Vehicle 100 includes an air conditioner 64, a DC/DC converter 62, anauxiliary device 68, and an auxiliary battery 66 as the device receivingsupply of electric power from battery 10. ECU 50 receives information ofconsumed electric power PAC from air conditioner 64.

Although an electric vehicle is shown as an exemplary vehicle in FIG. 1,the charging device for a vehicle-mounted battery disclosed in thepresent embodiment may also be applied to a vehicle that includes aninternal combustion engine in addition to battery 10 and motor generator30 such as a plug-in hybrid vehicle, as long as the vehicle is capableof having the vehicle-mounted battery to be charged from a sourceexternal to the vehicle.

FIG. 2 is a diagram to describe a configuration of the vehicle relatedto cooling of the power storage device in FIG. 1.

Referring to FIG. 2, the air drawn in by a fan 72 from the vehiclecompartment or luggage room or from outside the vehicle via an intakeport 70 passes through the interior of a case 74 to cool battery 10. Theair absorbing the heat of battery 10 is discharged from a discharge port76. An intake air temperature sensor 45 is provided at the air channelbetween fan 72 and case 74. The measured intake air temperature TA istransmitted to ECU 50 of FIG. 1. Further, temperature TB is measured bytemperature sensor 46 that detects the temperature of battery 10. Themeasured temperature TB is transmitted to ECU 50. Although battery 10may be a capacitor or the like as long as it can store electric energy,an example based on a battery will be described hereinafter.

Electric vehicles and plug-in hybrid vehicles that run using theelectric power from the battery rather frequently may require rapidcharging. For example, there is the case where the battery is chargedduring a long-distance travel. The state where the charging current isgreat will continue when rapid charging is carried out. In comparison,when the vehicle is running, the state where the discharging current isgreat will not continue so long even if the peak current value is high.Therefore, the amount of heat generated is greater during rapid chargingthan during running. If the cooling device of the vehicle is designed tocomply with the generated amount of heat in rapid charging, the coolingdevice will become greater in size and weight, which is not practical.Thus, it is expected that the temperature of the battery will becomehigh even if the cooling device is operated during rapid charging.

For the purpose of suppressing degradation in the lifetime of thebattery, the charging and discharging of the battery is restricted whenthe battery temperature becomes high. Therefore, if the batterytemperature rises greatly at the time of rapid charging, subsequentvehicle running will be limited. Measures must be taken in the chargingmethod to avoid the occurrence of such limitation in running.

FIG. 3 is a flowchart to describe the process of the charging methodexecuted in the first embodiment. In the first embodiment, the possiblerising temperature is set based on the temperature difference ΔT betweena limitation start temperature Tlim and the battery temperature TB inrapid charging to determine the charging rate in rapid charging. As willbe shown in FIG. 5 afterwards, limitation start temperature Tlim is thetemperature when the battery charging and discharging will be limited inthe case where battery temperature TB reaches that temperature.

Referring to FIG. 3, upon initiation of the process, the current batterytemperature TB and intake air temperature TA are obtained at step S1. Atstep S2, the current battery temperature TB is subtracted from thelimitation start temperature Tlim to obtain temperature difference ΔT,as in the following equation (1).

ΔT=Tlim−TB  (1)

At step S3, a determination is made as to whether the sum of thepredetermined temperature ΔT1 that rises in rapid charging andtemperature ΔT2 that rises in vehicle-running is larger than ΔT or notby the following equation (2).

ΔT<ΔT1+ΔT2  (2)

In the first embodiment, it is assumed that temperature ΔT1 andtemperature ΔT2 are fixed values. For example, temperature ΔT1 may beset as the temperature increasing width corresponding to the rise of thebattery temperature when rapid charging is carried out until the batterySOC becomes 100% from the state of 0%. Temperature ΔT2 can be set as thetemperature increasing width corresponding to the rise of the batterytemperature when the vehicle is made to run at the maximum power untilthe battery SOC becomes 0% from the state of 100%.

When equation (2) is not met at step S3, control proceeds to step S4.When equation (2) is met at step S3, control proceeds to step S5. Atstep S4, the charging current is set at the defined value for usualrapid charging. At step S5, a limited charging current is determinedbased on temperature difference ΔT and intake air temperature TA.

FIG. 4 represents an exemplary map employed in determining the chargingcurrent at step S5.

Referring to FIG. 4, when intake air temperature TA=40° C. in the casewhere ΔT=T1, the charging current is determined as charging currentI=Ic1.

The margin before reaching limitation start temperature Tlim becomesgreater as ΔT becomes larger. Therefore, the level of charging currentcan be set higher as a function of a larger ΔT.

Furthermore, the cooling of the battery allows the level of the chargingcurrent to be increased as a function of a lower TA. Therefore, in thecase where ΔT is equal, the level of the charging current can be sethigher when TA=20° C. than when TA=40° C. More data corresponding todifferent intake air temperatures (data other than TA=20° C., 40° C.)may be added to the map of FIG. 4.

Referring to FIG. 3 again, following the determination of the chargingcurrent at step S4 or step S5, battery charging at the determinedcharging current is executed at step S6, and the process ends at stepS7.

FIG. 5 represents the comparison in the rise of the battery temperaturebetween the case where charging is carried out by the charging method ofthe present invention and the case where charging is carried out withoutapplying the present invention.

In FIG. 5, the battery temperature is indicated along the vertical axis,and time is indicated along the horizontal axis. The solid linerepresents the change in battery temperature TB corresponding to thecase where the present invention is applied. The broken line representsthe change in battery temperature TB corresponding to the case wherecommon rapid charging is carried out. Limitation start temperature Tlimrepresents the temperature where the battery charging and discharging islimited by ECU 50 when battery temperature TB reaches the relevanttemperature. This limitation start temperature Tlim is set appropriatelyso that the battery lifetime is not significantly shortened bycharging/discharging carried out at high temperature. In other words,the vehicle presented in the present embodiment is configured toincrease the restriction on the electric power that is charged to ordischarged from the battery according to the rise of battery temperatureTB, in the case where battery temperature TB exceeds the predeterminedlimitation start temperature Tlim.

Following the charging at time t0-t1, the vehicle runs during timet1-t2. Since current flows to the battery during both charging andrunning, the battery generates heat to cause battery temperature TB torise. Thereafter, rapid charging carried out at a charging station orthe like during time t2-t3, t4-t5, t6-t7, and t8-t9 and dischargingcaused by running during time t3-t4, t5-t6, t7-t8, t9 and on arerepeated.

During the period of time t1-t4, the broken line and solid line matchsince battery temperature TB has sufficient margin against limitationstart temperature Tlim. In other words, usual rapid charging is carriedout during time t0-t1 and time t2-t3. In consideration of thetemperature rise and the like by charging at time t4, it is expectedthat there will be no margin against limitation start temperature Tlim.Therefore, during time t4-t5, charging is carried out at a charging ratelower than that of usual rapid charging in order to avoid limitation onthe running performance. Therefore, the charging completion time t5 inthe waveform indicated by the solid line is behind the chargingcompletion time in the waveform indicated by the broken line (the pointwhere the temperature turns downwards from increase).

Similarly, since the charging during time t6-t7 and t8-t9 has a lowercharging rate, the charging time in the waveform indicated by the solidline is longer than that in the waveform indicated by the broken line.However, since the occurrence of battery temperature TB reachinglimitation start temperature Tlim is avoided, as indicated by the brokenline waveform, the event of the running performance being limited or thecharging being limited can be avoided.

Thus, although the time required for charging will become longer more orless, the event of operating the cooling fan to wait for the battery tocool down in order to restore the running performance can be avoided.

Second Embodiment

FIG. 6 is a flowchart to describe the process in the charging methodexecuted in the second embodiment. In the second embodiment, risingtemperature ΔT1 is set based on a difference ΔSOC between a full-chargeamount and the current amount of charge, in addition to the temperaturedifference ΔT between limitation start temperature Tlim and batterytemperature TB in rapid charging, to determine the charging rate forrapid charging.

Referring to FIG. 6, upon initiation of the process, the current batterytemperature TB and intake air temperature TA are obtained at step S11.At step S12, the current battery temperature TB is subtracted from thelimitation start temperature Tlim, as in the following equation (1) toobtain temperature difference ΔT, similar to the first embodiment.

ΔT=Tlim−TB  (1)

At step S13, the current SOC of battery 10 is obtained. SOC is detectedby a known method based on the accumulated value of current IB and/orvoltage VB.

At step S14, the amount of charge ΔSOC that can be charged to attain afull-charge amount level from the current amount of charge level isobtained as shown in equation (3). SOCmax is the amount of charge setfor a full-charge amount state (the SOC upper limit value of charging).

ΔSOC=SOCmax−SOC  (3)

Further at step S14, temperature ΔT1 corresponding to the rise of thebattery temperature when the charging corresponding to ΔSOC obtained bythe calculation is applied to vehicle-mounted battery 10 in rapidcharging. For example, the data of temperature rise width ΔT1 ismeasured for each ΔSOC in advance and stored in a map.

At step S14, temperature ΔT1 is to be obtained by referring to this map.

At step S15, a determination is made as to whether the sum oftemperature ΔT1 obtained at step S14 and temperature ΔT2 that rises invehicle-running is larger than ΔT or not by the following equation (2),likewise with the first embodiment.

ΔT<ΔT1+ΔT2  (2)

In the second embodiment, it is assumed that temperature ΔT2 is a fixedvalue. For example, temperature ΔT2 can be set as the temperatureincreasing width corresponding to the rise of the battery temperaturewhen the vehicle is made to run at the maximum power until the batterySOC becomes 0% from the state of 100%.

When equation (2) is not met at step S15, control proceeds to step S16.When equation (2) is met at step S15, control proceeds to step S17. Atstep S16, the charging current is set at the defined value for usualrapid charging. At step S17, a limited charging current is determinedbased on temperature difference ΔT and amount of charge ΔSOC.

FIG. 7 represents an exemplary map employed in determining the chargingcurrent at step S17.

Referring to FIG. 7, when ΔT=T1, T2 and T3 in the case where ΔSOC=100%,the charging current is determined as charging current I=I1, I2, I3(100%), respectively.

There is a greater margin against limitation start temperature Tlim asΔT is larger. Therefore, the level of the charging current can be sethigher as a function of a larger ΔT.

In the case where ΔT=T3, the charging current is determined such ascharging current I=I3 (100%), I3 (50%) and I3 (30%) when the amount ofcharge is ΔSOC=100%, 50% and 30%, respectively.

Since the amount of electric energy to be charged rapidly becomesgreater as the ΔSOC becomes larger, the generated heat by the batteryalso becomes greater. Therefore, when temperature difference ΔT isequal, the level of charging current IB is set smaller as a function ofa larger ΔSOC to suppress temperature increase in order to accommodatethe vehicle running operation after charging.

Referring to FIG. 6 again, upon determining the charging current at stepS16 or step S17, the battery is charged by the determined chargingcurrent at step S18, and the process ends at step S19.

The second embodiment takes into consideration the amount of chargeΔSOC. Therefore, even in the case where the amount to be charged beforea fully charged state varies due to the running duration or runningdistance, limitation of the charging current is executed taking intoaccount the variation. The charging current can be set to a levellimited such that continuing the running operation is not disturbed.Therefore, the time required for charging become shorter than that ofthe first embodiment. Although the second embodiment has been describedbased on the case where the charging current is determined based ontemperature difference ΔT and charging amount ΔSOC, the charging currentmay be determined taking into account intake air temperature TA, as inthe first embodiment.

Third Embodiment

FIG. 8 is a flowchart to describe the process in the charging methodexecuted in the third embodiment. In the third embodiment, the possibleincreasing temperature is set based on a temperature difference ΔTbetween limitation start temperature Tlim and battery temperature TB inrapid charging to determine the charging rate for rapid charging. Atthis stage, a temperature increase expected value ΔT2 in vehicle-runningis set variable based on the running destination information, as well asinformation of the average current during the previous runningoperation, and the like to determine whether to limit the charging rateor not.

Referring to FIG. 8, upon initiation of the process, the current batterytemperature TB is obtained at step S21. At step S22, the current batterytemperature TB is subtracted from the limitation start temperature Tlimto obtain temperature difference ΔT, as in the following equation (1),likewise with the first and second embodiments.

ΔT=Tlim−TB  (1)

At step S23, the temperature increasing during vehicle running ΔT2 isdetermined. In the first and second embodiments, temperature ΔT2 was setat a fixed value taking into consideration the battery temperatureincrease corresponding to the case where the vehicle motor was driven atthe highest load for a long period of time. However, if it is known inadvance that such driving will not be carried out, the level of thecharging current may be increased to allow the charging period of timeto be shortened.

For example, if the destination is set at a navigation device 6 of FIG.1, what kind of road the vehicle will run after the charging stationwhere the vehicle stops over for charging can be identified.Accordingly, ΔT2 is set at a high value in the case where the roadincludes an uphill or in the case where the distance up to the nextcharging station is far. Furthermore, in the case where the destinationis close to the current location, or when the road towards thedestination is flat from the current location, ΔT2 is set smaller thanthe aforementioned case.

Moreover, ΔT2 may be determined based on the actual running history. Forexample, ΔT2 can be determined by equation (4) set forth below based onthe average current I from the previous charging to the current chargingand battery temperature TB.

ΔT2=I ² ×R(TB)/C  (4)

R (TB) represents the internal resistance of the battery at batterytemperature TB, and C represents the heat capacity of the battery pack.

Further, ΔT2 can be determined by the following equation (5) uponobtaining the required average power P by calculating the average roadload based on the average vehicle speed from the previous charging tothe present charging.

ΔT2=(P/V)² ×R(TB)/C  (5)

V represents the expected average voltage of the battery; R (TB)represents the internal resistance of the battery at battery temperatureTB; and C represents the heat capacity of the battery pack.

Various modifications are possible for calculating ΔT2. As analternative to or in addition to the aforementioned example, variationin the battery cooling performance, variation in the cooling air and thelike according to the average acceleration, vehicle speed area, and/orwhether the air conditioner is operated or not may be taken intoaccount.

At step S24, a determination is made as to whether the sum of thepredetermined temperature ΔT1 that rises in rapid charging andtemperature ΔT2 determined at step S23 is larger than ΔT or not by thefollowing equation (2), likewise with the first and second embodiments.

ΔT<ΔT1+ΔT2  (2)

When equation (2) is not met at step S24, control proceeds to step S25.When equation (2) is met at step S24, control proceeds to step S26. Atstep S25, the charging current is set at the defined value for usualrapid charging. At step S26, a limited charging current is determinedbased on temperature difference ΔT.

Upon determination of the charging current at step S25 or step S26, thecharging towards the battery is executed at step S27 at the determinedcharging current, and the process ends at step S28.

Setting the battery increase temperature ΔT2 in vehicle-running variableas described in the third embodiment may be combined with the first orsecond embodiment. Accordingly, the charging current and chargingduration can further be optimized.

It should be understood that the embodiments disclosed herein areillustrative and non-restrictive in every respect. The scope of thepresent invention is defined by the terms of the claims, rather than thedescription of the embodiments set forth above, and is intended toinclude any modifications within the scope and meaning equivalent to theterms of the claims.

REFERENCE SIGNS LIST

-   -   2 power supply; 4 charger; 6 navigation device; 10 battery; 20        inverter; 30 motor generator; 35 driving wheel; 37 wheel speed        sensor; 42 voltage sensor; 44 current sensor; 45 intake air        temperature sensor; 46 temperature sensor; 60 display device; 62        DC/DC converter; 64 air conditioner; 66 auxiliary battery; 68        auxiliary device; 70 intake port; 72 fan; 74 case; 76 discharge        port; 100 electric powered vehicle.

1. A charging device for charging a battery mounted on a vehicle by anexternal power supply, said vehicle configured to increase limitation onelectric power charged to and discharged from said battery according toincrease in temperature of said battery when said battery temperatureexceeds a predetermined temperature, said charging device comprising: atemperature sensor for detecting the temperature of said battery, acharger receiving electric power from said external power supply tocharge said battery, and a control device controlling said charger suchthat said battery is charged at a charging rate determined based on atemperature difference between said predetermined temperature and saidbattery temperature, said vehicle on which said battery is mounted beingcapable of repeatedly executing a charging operation towards saidbattery from outside the vehicle and a vehicle-running operation, saidcontrol device determining said charging rate based on a temperatureincrease expected amount when said vehicle runs next time and saidtemperature difference.
 2. The charging device according to claim 1,wherein said control device determines said charging rate based on adifference between an amount of charge corresponding to full charge ofsaid battery and a current remaining amount of charge, and saidtemperature difference.
 3. (canceled)
 4. A charging method for charginga battery mounted on a vehicle by an external power supply, said vehicleconfigured to increase limitation on electric power charged to anddischarged from said battery according to increase in temperature ofsaid battery when said battery temperature exceeds a predeterminedtemperature, said charging method comprising the steps of: detecting atemperature of said battery, calculating a temperature differencebetween said predetermined temperature and said battery temperature, andcharging said battery such that charging of said battery is executed ata charging rate determined based on said temperature difference, saidvehicle on which said battery is mounted being capable of repeatedlyexecuting a charging operation towards said battery from outside thevehicle and a vehicle-running operation, said step of chargingdetermining said charging rate based on a temperature increase expectedamount when said vehicle runs next time and said temperature difference.5. The charging method according to claim 4, wherein said step ofcharging determines said charging rate based on a difference between anamount of charge corresponding to full charge of said battery and acurrent remaining amount of charge, and said temperature difference. 6.(canceled)